1. Field of the Invention
The present invention relates to an apparatus and a method for controlling operation of a reciprocating compressor. In particular, the present invention relates to an apparatus and a method for controlling operation of a reciprocating compressor that is capable of reducing a stroke estimation error by estimating a stroke with a counter electromotive force induced by a searching coil and removing an error due to resistance and inductance in a compressor motor (hereinafter, referred to as a motor).
2. Description of the Prior Art
FIG. 1 is a block diagram illustrating an operation control apparatus of a reciprocating compressor in accordance with the conventional art. As depicted in FIG. 1, the operation control apparatus of the reciprocating compressor includes a current detector 150 for detecting current applied to a motor; a voltage detector 140 for detecting a voltage applied to the motor; a stroke estimator 130 for estimating a stroke on the basis of the detected current, voltage and a motor constant; a comparator 100 for comparing the estimated stroke with a preset stroke reference value and outputting a difference value according to the comparison result; and a controller 110 for controlling a stroke of the compressor by varying a voltage applied to the motor according to the difference value.
Hereinafter, the operation of the control apparatus of the reciprocating compressor will be described with reference to accompanying FIG. 2.
First, the current detector 150 detects current applied to the motor, and the voltage detector 140 detects a voltage applied to the motor. Herein, the stroke estimator 130 calculates a stroke estimation value of the compressor with Equation 1 by substituting the detected current value, the detected voltage value and a motor constant and applies the calculated stroke estimation value to the comparator 100.
                    X        =                              1            α                    ⁢                      ∫                                          (                                                      V                    M                                    -                  Ri                  -                                      L                    ⁢                                                                                  ⁢                                          i                      _                                                                      )                            ⁢                              ⅆ                t                                                                        Equation        ⁢                                  ⁢        1            
Herein, R is the resistance of the motor, L is the inductance of the motor, α is a motor parameter, VM is the voltage of the motor and i is the current of the motor.
Then, the comparator 100 compares the stroke estimation value with the stroke reference value (S220) and applies a difference value according to the comparison result to the controller 110. The controller 110 controls a stroke by varying the voltage applied to the motor on the basis of the difference value.
In more detail, the control unit 110 increases a motor supply voltage (S240) when a stroke reference value is greater than a stroke estimation value, and the control unit 110 decreases a motor supply voltage (S230) when a stroke reference value is less than a stroke estimation value.
However, in the conventional operation control method of the reciprocating compressor, because stroke control is performed by estimating a stroke utilizing all motor parameters (motor constant, resistance, inductance, etc.), an error in an estimated stroke is increased due to errors and non-linearity of the parameters.